With the LCDs applied to more and more fields, the LCDs have a trend to become larger in size, which means larger viewing area and high definition. Generally, LCDs employing thin film transistors (TFTs), which are called TFT-LCDs, have a problem of gate delay due to the long gate lines. Gate delay usually results in image flicker or other problems.
Referring to FIG. 3, a typical LCD 100 includes a scanning driver 110, a data driver 120, and a liquid crystal panel 130. The scanning driver 110 is configured for providing a plurality of scanning signals to the liquid crystal panel 130, and the data driver 120 is configured for providing a plurality of gray scale voltages to the liquid crystal panel 130.
The liquid crystal panel 130 includes a plurality of gate lines 101 parallel to each other, a plurality of data lines 102 which are parallel to each other and intersect the gate lines 101, a plurality of TFTs 103 arranged at each cross of the gate line 101 and the data line 102, a plurality of pixel electrodes 104, and a plurality of common electrodes 105 opposite to the pixel electrodes 104. A minimal area constituted by two adjacent gate lines 101 and two adjacent data lines 102 is defined as a pixel area. The scanning driver 110 outputs a plurality of scanning signals to the gate lines 101 sequencially. The data driver 120 applies a plurality of gray scale voltages to the pixel electrodes 104 through corresponding TFTs 103 when a gate line 101 is scanned.
Referring also to FIG. 4, an equivalent circuit diagram of a pixel area is shown. A gate electrode 1031 of the TFT 103 is connected to the gate line 101, a source electrode 1032 is connected to the data line 102, and a drain electrode 1033 is connected to the pixel electrode 104. Because the gate line 101 has a certain resistance R itself, and a parasitic capacitance Cgd is generated between the gate electrode 1031 and drain electrode 1033, thus, an RC delay circuit is generated thereat. In one gate line 101, therefore, many such RC delay circuits are connected in series. The RC delay circuit can delay the scanning signal applied to the gate line 101, thus the waveform of the scanning signal can be distorted. That is, a square waveform of the scanning signal may not be the same square waveform when reaching a tail end of the gate line 101.
Referring also to FIG. 5, waveforms of the scanning signal adjacent to the scanning driver 110 and far from the scanning driver 110 are shown. “Vg1” denotes a waveform of the scanning signal of one gate line 101 that is at a front end adjacent to the scanning driver 110, and “Vg2” denotes a waveform of the scanning signal of the gate line 101 that is at a tail end distal from the scanning driver 110. That is, the waveform “Vg2” represents the distorted waveform of the scanning signal which is delayed by the serial RC delay circuits. “Von” denotes a turn-on voltage of the TFT 103, and “Voff” denotes a turn-off voltage of the TFT 103. Because of distortions of the waveform of the scanning signal, the TFT 103 is delayed to be turned on, for example, “t1” seconds as shown in FIG. 3. That is, an activated on-state period of time of the TFTs 103 away from the scanning driver 110 is shorter than it is supposed to be.
Because a gray scale voltage is not be applied to the pixel electrode 104 until the corresponding TFT 103 is turned on, the pixel electrode 104 which is away from the scanning driver 110 is lack of charging of the gray scale voltage. Thus, the display image is deteriorated in the corresponding pixel area. Actually, many pixel areas are affected because the corresponding TFTs 103 lack of charging of gray scale voltages. In this case, the image of the LCD 100 has flickers.
What is more, the TFTs 103 adjacent to the tail end can also be delayed to turned off by the distorted waveform of the scanning signal, for example, “t2” seconds as shown in FIG. 3. That is, when a next gate line 101 is scanned, some TFTs 130 connected to the former gate line 101 are still turned on. At this circumstance, gray scale voltages supposed to supply to the next pixel electrodes 104 are also applied to the adjacent former pixel electrodes 104 adjacent to the tail end. In this case, the image of the LCD 100 appears flickers.
What is needed, therefore, is a liquid crystal display and driving method for the liquid crystal display which can overcome the above-described deficiencies.